One of the papers we had to read in my current class (CS523, Advanced Operating Systems) caught my attention and presents some very interesting possibilities.

http://www.cs.washington.edu/homes/levy/opal/opal.htm (1994)

Opal, a shared memory system, describes a flat memory system that provides centralized management of the memory resources without requiring applications to maintain their own address space. Though not specifically described in the paper, this system could be developed to act as a completely separate system to provide a shared memory address space for multiple applications on one computer, and possibly multiple applications on multiple computers.

Consider the conceptual change of a computer system with a memory system that isn't under the direct control of the machine's processor. Problems that this would create are many, but I think that new possibilities are equally numerous.